This invention relates generally to waste water treatment and more particularly concerns the treatment of hazardous waste waters such as the effluent water discharged from hydrocarbon processing facilities, general industrial facilities or contaminated municipal water supplies.
The effluent water discharging from a hydrocarbon processing facility contains oil components, phenols, gas components such as H2S and NH3. Similarly, chemical and industrial processes use water in their operations for cooling, quenching, pH adjustment and washing of various hydrocarbon streams, usually resulting in the creation of an effluent water stream containing inorganic and organic contaminants. Tank farm operations, marine facilities and ships contain effluent water and soil and ground water reservoirs are occasionally contaminated by oil and chemical spills.
The Federal Resource Conservation and Recovery Act (RCRA) of 1976 has focused the attention of both industry and government on the problems of land and water way disposal of untreated hazardous waste from industrial facilities, including hydrocarbon processing facilities and oil and gas operating facilities, and encouraged the development of alternative hazardous waste treatment technologies to immobilize and/or destroy the waste either in situ, in previously disposed waste or at the waste generation site. More recent federal legislation, such as the Comprehensive Environmental Response Compensation and Liability Act (CERCLA) of 1980, encourages the development and adoption of hazardous waste treatment and destruction processes that would eventually eliminate the need for land disposal of hazardous waste including water effluent from hydrocarbon processing facilities, except for the disposal residues from treatment operations. Despite the focused attention on the problems, various studies estimate such hazardous waste is generated by the petroleum refining industry at a rate of more than one million tons per year.
The biological treatment of waste streams is based on the ability of a mixed population of microorganisms to utilize organic contaminants as nutrients. The two major classes of known biological treatments are aerobic with oxygen and anaerobic without oxygen. Because biological systems contain living organisms, they require specific ratios of carbon and nutrients. Most organisms function within a relatively neutral pH range between 6.0 and 8.0. High concentrations of toxic and organic substances such as cyanide, arsenic, and heavy metal ions and solutions such as copper, lead and zinc inhibit enzyme formation in the microorganisms and eventually kill them. Consequently, some waste streams are not treatable by known biological treatment processes.
Wet air oxidation, generally considered to be a pre-treatment process, is used to economically treat aqueous wastes containing both organic and inorganic toxics in waste streams too dilute to incinerate and too toxic to biotreat. The process alters chemical structure by low temperature oxidation of the waste so that toxic compounds become nontoxic. In known wet air oxidation processes, depending on the waste, the off gas may have to be scrubbed or otherwise treated to remove any low molecular weight hydrocarbons present. If an ionic catalyst must be added to the reactor to improve conversion efficiency, a catalyst regenerator must be added to the process. Elevated temperatures ranging from 175-325° C. and residence times ranging from 60-120 minutes are typically required for oxidation of the waste. Most problematic is that process pressure must be maintained between 300-3000 psig to prevent excessive evaporation of liquid. And the typical construction materials appropriate for wet air oxidation reactors are stainless steel, nickel and titanium alloys.
Chemical oxidation has been found to be effective in the treatment of certain industrial and domestic wastewater and is one of the few processes for removing odor, color and various potentially toxic organic substances such as phenolics, pesticides and industrial solvents. It also disinfects tranquil water by killing or inactivating pathogenic microorganisms that may be present. The chemical oxidants employed include chlorine, chlorine dioxide, ozone and hydrogen peroxide. Known chemical oxidation processes involve a relatively high operating cost and the chemicals used are consumed in the process.
It is, therefore, an object of this invention to provide a process and apparatus useful to treat effluent from hydrocarbon processing facilities. It is also an object of this invention to provide a process and apparatus useful to permit the effluent water discharging from a hydrocarbon processing facility to be recycled or reused. A further object of this invention is to provide a process and apparatus useful to permit the effluent water discharging from a hydrocarbon processing facility to be recycled without treatment at a wastewater disposal plant. Still another object of this invention is to provide a process and apparatus useful to treat effluent from a hydrocarbon processing facility at the facility. Another object of this invention is to provide a process and apparatus useful to treat hazardous wastes that have already entered the water table or landfills. Yet another object of this invention is to provide a process and apparatus useful to immobilize and/or destroy previously disposed waste in situ. An additional object of this invention is to provide a process and apparatus useful to reduce the need for land disposal of hazardous waste other than the disposal residues from treatment operations. It is also an object of this invention to provide a process and apparatus useful to treating a wide range of waste streams. A further object of this invention is to provide a process and apparatus characterized by economically feasible pressure, temperature and residence time requirements in hazardous waste treatment applications. And it is an object of this invention is to provide a process and apparatus characterized by optimized rates of chemical and energy consumption in the treatment of hazardous waste.